The chloroplast is bounded by a double membrane layer. There are two distinct regions present inside the chloroplasts. One is grana while the other is stroma. Grana is made up of stacks of disc-shaped structures known as thylakoids. These contain the molecule chlorophyll and are the functional units of chloroplasts. Stroma is the matrix which contains grana and is similar to the cytoplasm in cells in which all the organelles are embedded. Stroma also contains various enzymes, DNA, ribosomes, and other substances. Stroma lamellae connect the stacks of thylakoid sacs. There are two types of reactions by which photosynthesis occur, light reaction and dark reaction. Light reaction occurs in grana while dark reaction takes place in the stroma of chloroplasts.Functions of Plastids\tChloroplasts have a structure called chlorophyll which trap solar energy and this is utilized to manufacture food for the plant.\tThe flowers have different colors because of the pigments called chromoplast. These colors attract insects for pollination.\tLeucoplasts are the colorless plastids which store food in the form of carbohydrates, fats, and proteins.